/*
 * Copyright 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import java.util.HashSet;
import java.util.Set;


/**
 * Converts String to a Boolean.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 3.0
 */
final class StringToBooleanConverter implements Converter<String, Boolean> {

    private static final Set<String> trueValues = new HashSet<String>(4);

    private static final Set<String> falseValues = new HashSet<String>(4);

    static {
        trueValues.add("true");
        trueValues.add("on");
        trueValues.add("yes");
        trueValues.add("1");

        falseValues.add("false");
        falseValues.add("off");
        falseValues.add("no");
        falseValues.add("0");
    }

    public Boolean convert(String source) {
        String value = source.trim();
        if ("".equals(value)) {
            return null;
        }
        value = value.toLowerCase();
        if (trueValues.contains(value)) {
            return Boolean.TRUE;
        } else if (falseValues.contains(value)) {
            return Boolean.FALSE;
        } else {
            throw new IllegalArgumentException("Invalid boolean value '" + source + "'");
        }
    }

}
